Among known printers such as label printers, thermal printers are widely used. The thermal printer transfers ink that is coated on an ink ribbon by heating and melting the ink with a thermal head. In such a printer, the ink ribbon is stretched between a ribbon holding shaft and a ribbon winding shaft, and an end of the winding shaft is rotated by a motor to feed the ribbon. This winding shaft is installed as a cantilever in which only one end of the winding shaft is driven by a driving motor. In this printer, twisting of the ink ribbon along a feeding direction may occur. There may be multiple factors for the twisting, and a combination of the multiple factors causes the ink ribbon to twist.
For example, when the motor is provided at one end of the ribbon winding shaft as described above, the winding shaft may become slightly deformed and may have a torque difference in accordance with the distance from the motor, because the winding shaft is elongated in the width direction of the ribbon. As a result, tension of the ribbon differs between a part of the ribbon in a side near the motor and a part of the ribbon in a side away from the motor, which can cause the ribbon to twist. Moreover, the ink ribbon may twist because of a difference in friction in the width direction of the ribbon when the ribbon is at a position in which the thermal head faces a platen, and a slight tilt relative to the feeding direction of the ribbon in a linear facing area of the thermal head and the platen. Furthermore, due to the above-described cantilever arrangement, a slight tilt of a mounting angle of the ribbon winding shaft or the ribbon holding shaft facilitates twisting of the ribbon. The ink ribbon that is twisted at a transferring position at which the thermal head contacts the ribbon, causes poor print quality.
The related art discloses a mechanism for adjusting tension of a ribbon between a winding shaft and a feeding shaft, but this mechanism does not prevent an ink ribbon from twisting.